1. Field of the Invention
The present invention relates to a seal construction for use in sealing a wheel support bearing assembly that includes two bearing elements rotating relative to each other. More particularly, the invention relates to a seal construction that includes a rotation detect device that may be used in conjunction with the wheel control system on an automotive vehicle for detecting the number of revolutions for each of the front and rear, left and right wheels on the automotive vehicle.
2. Prior Art
A conventional wheel rotation detect apparatus is often used with the anti-locking/skidding system that is designed to prevent the wheel locking or skidding on an automotive vehicle, and includes an encoder that is actuated magnetically to generate pulses, and a sensor that is disposed to face opposite the encoder for sensing the pulses from the encoder. An example of such a wheel rotation detect apparatus is disclosed in the French patents Nos. 2558223 and 2574501.
The wheel rotation detect apparatus disclosed in the above French patents is usually used in conjunction with a sealing device that is provided for sealing the wheel support bearing assembly. Recently, the wheel rotation detect apparatus has been developed as a seal with integrated sealing and rotation measuring capabilities, and has been used for practical purposes. More recently, the sealing device has been developed as a combination seal that consists of a plurality of sealing members that provide high sealing capability. The encoder that may be used with such sealing device has become larger in size for those recent years.
By referring now to FIG. 3, a typical example of such a seal with integrated sealing and rotation measuring capabilities will be described below. The seal with integrated sealing and rotation measuring capabilities is installed on the wheel support bearing assembly on an automotive vehicle that includes a rotational bearing element 1 and a non-rotational bearing element 2 rotating relative to each other, and provides sealing capability for the bearing assembly as well as the capability of detecting the number of revolutions for the wheel.
More specifically, this seal is provided in the form of a combination seal that includes a metallic slinger 22 having an L-shape cross section and a metallic seal ring 25. The slinger 22 includes a cylindrical portion 20 extending axially and adapted to be secured to the rotational bearing element 1, and a flanged portion 21 extending from the axial outside toward the radial outside of the cylindrical portion 20. The seal ring 25 includes a cylindrical portion 23 extending axially and adapted be secured to the non-rotational bearing element 2 and a flanged portion 24 extending from the axial inside toward the radial inside of the cylindrical portion 23. The seal ring 24 further includes an elastic seal lip having its tip adapted to make sliding contact with the side of the slinger 22 facing opposite to the seal ring 25. In the embodiment shown in FIG. 3 that is conventional in this field, the elastic seal lip includes a radial lip 26, 27 extending diagonally toward the radial inside and toward the axial inside or outside, and an axial lip 28 extending diagonally toward the radial outside and toward the axial outside. An encoder 16 actuated magnetically for generating pulses is provided on the flanged portion 21 of the slinger 22, and a sensor 17 is located to face opposite to the encoder 16 for sensing the pulses from the encoder 16.
In the conventional seal with the integrated sealing and rotation measuring capabilities shown in FIG. 3 and described above, the encoder 16 and sensor 17 are located on the outermost side of the seal where they are exposed to the atmosphere. Thus, the encoder 16 and sensor 17 are always placed directly under unfavorable circumstances in which they can be affected by any splashing water or foreign matter. If the water should enter the seal with the integrated sealing and rotation measuring capabilities, it might cause rust to gather on the metal parts of the seal that would degrade the rotation detect capability. What is worse is that there is even the possibility that foreign matter might be attached to the parts of the seal. If any foreign matter could enter the area between the encoder 16 and sensor 17 where the foreign matter should be attached to the encoder 16 and/or sensor 17, the encoder 16 and/or sensor 17 might be damaged by the foreign matter biting the encoder 16 and/or sensor 17 during rotation of the wheel support bearing assembly. If this should occur, the rotation detection section composed of the encoder and sensor would not be able to detect the number of revolutions accurately, which would be a serious problem.
In most cases, the encoder 16 is attached to the flanged portion 21 of the slinger 22 that provides the sealing action, which imposes limitations on the choice of the material and shape of the encoder.